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    What is the best way to know how much time is on an engine since major overhaul? Hobbs meter? Thanks!

  • #2
    Originally posted by Tina Gonsalves View Post
    What is the best way to know how much time is on an engine since major overhaul? Hobbs meter? Thanks!
    It's measured two ways, hours by tach, and time by calendar. Overhaul intervals (not required to be observed by Part 91 operators) are stated both as hours and time.

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    • #3
      What is the best way to know how much time is on an engine since major overhaul? Hobbs meter?
      Everything Scott said, and ... The Hobbs measures the amount of real time the master switch is on. It's just an electric clock. Tach "time" is actually a count of engine revolutions translated to approximate time, and so is a more accurate indication of engine usage -- slower at idle and taxi, faster at full power. It's calibrated to read one hour at normal operating RPM times 60. Thus, if normal operating RPM is assumed to be 2400 for a particular engine, the tach should read one "hour" after counting 2400 * 60, or 144,000 crankhshaft revolutions.

      Hate is a self-built dungeon in which a man imprisons his own soul.

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      • #4
        Originally posted by Ray Tackett View Post

        Everything Scott said, and ... The Hobbs measures the amount of real time the master switch is on. It's just an electric clock.
        Often in twins the Hobbs is on a landing gear squat switch and is measuring flight time. Or it might be on an oil pressure sensor to measure time when the engine is running.

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        • #5
          So. The reason that I've asked is that I have an interested party looking to purchase the share of the plane vacated by my partner who passed away last year. He asked, how much time is on the engine SMOH. Tach time is accurate for TT on the air-frame, from what I understand. (When the tach was replaced, the hours were transferred onto the new one.)

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          • #6
            Originally posted by Tina Gonsalves View Post
            So. The reason that I've asked is that I have an interested party looking to purchase the share of the plane vacated by my partner who passed away last year. He asked, how much time is on the engine SMOH. Tach time is accurate for TT on the air-frame, from what I understand. (When the tach was replaced, the hours were transferred onto the new one.)
            So tell him/her the tach time elapsed since the OH plus when the last OH was done.

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            • #7
              hours SMOH should be clearly indicated in the engine logbook. Sometimes I have seen SFOH if the factory did the overhaul.

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